Circadian rhythms of agitation in institutionalized patients with Alzheimer's disease

Agitation is a common problem in institutionalized patients with Alzheimer' s disease (AD). "Sundowning," or agitation that occurs primarily in the eve ning, is estimated to occur in 10-25% of nursing home patients. The current study examined circadian patterns of agitation in 85 patients with AD livi ng in nursing homes in the San Diego, California, area. Agitation was asses sed using behavioral ratings collected every 15 minutes over 3 days, and ac tivity and light exposure data were collected continuously using Actillume recorders. A five-parameter extension of the traditional cosine function wa s used to describe the circadian rhythms. The mean acrophase for agitation was 14:38, although there was considerable variability in the agitation rhy thms displayed by the patients. Agitation rhythms were more robust than act ivity rhythms. Surprisingly, only 2 patients (2.4%) were "sundowners." In g eneral, patients were exposed to very low levels of illumination, with high er illumination during the night being associated with less robust agitatio n rhythms with higher rhythm minima (i.e., some agitation present throughou t the day and night). Seasonality was examined; however, there were no cons istent seasonal patterns found. This is the largest study to date to examin e agitation rhythms using behavioral observations over multiple 24h periods . The results suggest that, although sundowning is uncommon, agitation appe ars to have a strong circadian component in most patients that is related t o light exposure, sleep, and medication use. Further research into the unde rstanding of agitation rhythms is needed to examine the potential effects o f interventions targeting sleep and circadian rhythms.